feance



Patented Nov. 21, 1922.

LAURENT EMILE MARIE TREVOUX, OF PETIT-QUEVILLY, FRANCE, ASSIGNOR TO LA SOCIETE ANONYME DE PRODUITS CHIMIQUES (ETABLISSEMENTS MALETRA), OF

PETIT-QUEVILLY, FRANCE.

PROCESS FOR THE PRODUCTION OF ACETALDEHYDE FROM ACETYLENE.

No Drawing.

To all whom it may concern:

Be it known that I, LAURENT EMILE MARIE Tnsvoux, citizen ofthe Republic of France, and resident of Petit-Quevilly, Seine Inferieure (post-oilice address 143 Route de Caen), France, have invented a new and useful Process for the Production of Acct-aldehyde from Acetylene, which improvements are fully set forth in the following specification.

A number of patents and processes exist for the production of acetaldehyde from acetylene, all of them based on the same re action, namely, the combining of acetylene with water by means of a catalyzing agent, a mercury saltgenerally in an acid medium. The only difference between these processes is with regard to the kind of mercury salt used, the nature and concentration of the acid, the temperature of reaction and the rate of supply of the acetylene gas.

The amount of aldehyde produced varies greatly, according to the way in which the operation is performed. The mercury salt used as catalyzer is gradually reduced and at the end of a certain time is entirely transformed into a greyish powder. At this point the reaction stops, and the formation of aldehyde ceases. The quantity of aldehyde produced would, therefore, appear to depend essentially on the. speed with which the reduction of the mercury salt is, effected.

In order to lower the cost of manufacturing the aldehyde, it is desirable to produce 20 times that weight.

v. The object of the present invention is a process for the production of acetaldehyde which enables the obtaining of much larger, and practically unlimited amounts of this aldehyde from a given weight of mercury.

The essential characteristic of this process consists in using, as catalyzer, metallic mercury to which has been added an oxidizing Application filed March 24, 1920. Serial No. 368,348.

substance adapted to impart to the mercury a special activity which enables it to form the mercury-aldehyde compound in a. stable condition, and maintain the catalyzing action of the contact substance indefinitely. If the catalyzer consists solely of mercury either in the state of metallic mercury or in the form of reduced mercury, no

absorption of the acetylene takes place.

The combination of the acetylene with water is effected by adding an oxidizing agent such as ferric oxide, and acetaldehyde can be prepared in unlimited quantities,

provided that a certain proportion of ferric oxide is maintained in the absorption liquor. The reaction does not stop until the added agent has lost its oxidizing power.

The mercury can therefore be used indefinitely as catalyzer, all that is necessary beall that is necessary being that the oxidizing power of the substance used should be sufficient to maintain the catalytic action of the catalyzer and that it should'decompose the intermediate compound of mercury aldehyde formed, but not oxidize the aldehyde.

lVith oxidizing agents that are too energetic, or with a substance capable of liberating oxygen in the nascent state, a negative result would be obtained, and the formation of aldehyde would be arrested.

In the present invention the catalyzer may be prepared in the following manner:

An intimate mixture of reduced mercury and of ferric oxide is prepared, the necessary acid and water for hydrating the acetylene being then added. If an excess of purified acetylene is introduced at a temperature of 80 C., and under suitable pressure, into the absorption apparatus, which is provided with a mechanical stirrer, the reaction begins, the

aldehyde compound is immediately formed and the aldehyde vapors are directly condensed in suitable refrigerating means.

The absorption of the acetylene proceeds in a very regular manner, and only ceases we when the ferric oxide has' been completely I transformed into ferrous oxide. If the v.

sorption liquid are added. The presence of a few globules of mercury in the liquid does not interfere with the reaction, as the mechanical agitation in the course of the reaction causes them to disa pear.

In order that the cata yzer of the present invention which consists of metallic mercury and an added oxidizing agent such as ferric oxide may exhibit the maximum activ'ity, a number of conditions require to be fulfilled.

The quantity of sulphuric acid used '1s preferably to of the mixture. With this proportion, coupled with a suitable temperature and a suitable flow of acetylene, an almost theoretical yield of pure aldehyde is obtained. An excessive sulphuric acid content leads to the formation of polymerization. products of aldehyde, (aldols, crotonaldehydes, tars). Similarly, an excessive rate 'of flow of the acetylene is detrimental to the satisfactory progress of the reaction, which being exothermic requires a certain equilib rium of temperature to be maintained. The purity of the gas also plays an essential part in the progress of the reaction. It has been found that the yield of aldehyde may vary considerably with the extent to which the impurities, especially phosphoretted hydrogen, in the gas have been removed. In order to be able to check at any moment the degree of purity of the gas, the gas after being washed with a purifying agent containing metallic oxichlorides, may be advantion of the catalyzer throughout the course tageously passed through a column containing a hydrochloric solution of mercuric chloride which is a very sensitive re-agent, for hydrogen phosphide.

Finally, the temperature of the reaction must be between and 83 C. Below 70 C. the absorption is slower, whilst above 83 C.-'polymerization begins and the residue after the operation contains a considerable amount of tars. 4

In order to maintain the same concentr of the process, the water necessary for the hydration of the acetylene is added'periodically at certain intervals in a quantity corresponding to the Weight of aldehyde formed during such intervals.

As in similar processes, energetic mechanical agitation is required in the absorption apparatus in order to mix the acetylene intimately with the contact substance.

Sulphuric acid may be replaced by 'another suitable acid such as a sulphonic acid, or part of the sulphuric acid may be replaced by a fatty acid, such as acetic acid which is a good solvent for acetylene.

With such an acid the reaction is much quicker and the absorption is intensified, so that it is more difiicult to avoid polymerization and the formation of tars.

The essential advantage of the process is that the mercury employed as catalyzer can be used indefinitely. In all the other processes, on the contrary, as soon as the mercury is reduced it has to be regenerated, an operation which is very expensive and is entirely dispensed with in the present invention. In the present process, the only substance which is periodically and systematically renewed is the ferric oxide, a substance which costs little, and can be easily separated from the mercury as soon as it is reduced to the ferrous state; whilst the mercury plays the part of a continuous catalyst.

As can be seen from the above the catalyzer used is mercury in the metallic or in the reduced state. However, without departing from the scope of the invention either mercuric oxide, in acid solution, or a mercuric salt, may take the place of the initial charge of mercury.

E wample In a suitable agitation apparatus 9.26 kilos of metallic mercury are triturated with 7.4 kilos of ferric oxide, 70 kilos of 100% sulphuric acid, and 191 kilos of water are added and the mixture is heated to 80 C. Thereupon, a suitable excess of acetylene is introduced under the necessary pressure, the temperature being maintained between 70 and 83 C. preferably at 80 during the reaction. The amount of water required for hydration, which corresponds to the weight of aldehyde obtained, 'is added at certain intervals so as to maintain a suitable content of water in the absorption liquor throughout.

In this way 280 kilos of acetic aldehyde are obtained.

As soon as all the ferric salt has been transformed into the ferrous state, 7 .4 more kilos of ferric oxide and 13.34 kilos of sulphuric acid are added to the absorption liquor. By continuing to work under the same conditions as described above, 280 more kilos of acetaldehyde are obtained.

Theoretically, this operation may be repeated almost to an unlimited extent by periodically renewing the acid ferric oxide solution.

If after a certain number of operations the absorption liquor should contain a small amount of tars, these latter are separated from the mercurial catalyzer, which is used again.

E wample 2.

A commencement is made with the reduced mercury obtained by the reduction of 10 kilos of mercuric oxide. This oxide may be reduced by means of a suitable organic reducing agent such as formaldehyde, acetaldehyde, sugar or the like. In this Way by using 10 kilos of mercuric oxide, 13.34 kilos of 100% sulphuric acid and 191 kilos of water, 200 to 210 kilos of aldehyde are obtained. At this point all the mercuric oxide will have been reduced. The liquid is decanted and 7.4 kilos of ferric oxide, 70 kilos of sulphuric acid and 191 kilos of water are added to the reduced mercury. The operation is then continued in the same way as in Examp e 1.

By this means 280 kilos of acetaldehyde are obtained.

By renewing the ferric oxide at every operation a fresh quantity of 280 kilos of acetaldeh de is obtained in each case.

What claim as new and desire to secure by Letters Patent of the United States is 1. A process for the production of acetaldehyde from acetylene, comprising hydrating acetylene in t e presence of a catalyzer consisting of a mixture of metallic mercury, a sulfur acid and an oxidizing agent capable of maintaining the catalyzing action of the mercury indefinitely; substantially as described.

2. A process for the production of acetaldehyde from acetylene, comprising hydratlng acetylene in the presence of a catalyzer consisting of a mixture of metallic mercury, a sulfur acid and ferric oxide; substantially as described.

3. A process for the production of acetaldehyde from acetylene, comprising hydrating acetylene in the presence of a catalyzer conslsting of a mixture of metallic mercury and an oxidizing agent capable of maintaining the catalyzing action of the mercury indefinitely, and adding concentrated sulphuric acid to obtain a theoretic yield of pure aldehyde and to avoid the formation of polymerization products of aldehyde; substantially as described.

4. A process for the production of acetal dehyde from acetylene, comprising hydrating acetylene in the presence of a catalyzer consisting of a mixture of metallic mercury and ferric oxide, and adding concentrated sulphuric acid to obtain a theoretic yield of pure aldehyde and to avoid the formation of polymerization products of aldehyde; substantially as described.

5. A process for the production of acetaldehyde from acetylene, comprising passing an excess of acetylene gas'in contact with an agitated mixture of metallic mercury and an oxidizing agent capable of maintaining the catalyzing action of the mercy indefinitely and containing concentrated sulphuric acid, maintaining the temperature of the mixture at between 70 and 83 0., and adding the Water necessary for the hydration of the acetylene at intervals cor responding to the weight of acetaldehyde formed during such intervals; substantially as described.

6. A process for the production of acetaldehyde from acetylene, comprising passing an excess of acetylene gas in contact with an agitated mixture of metallic mercury and ferric oxide, maintaining the temperature of the mixture at between 70 and 83 C., and adding the water necessary for the hydration of the acetylene at intervals corresponding to the weight of acetaldehyde formed during such intervals; substantially as described.

7. A process for the production of acetaldehyde from acetylene, comprising passing an excess of acetylene gas in contact with an agitated mixture of metallic mercury and concentrated sulphuric acid and water, maintaining the temperature of the mixture at between 70 and 80 C., and gradually adding an oxidizing agent capable of maintaining the catalyzing action of the mercury indefinitely, at certain intervals and at the rate at which the the oxidizing agent is reduced.

8. A process for the production of acetaldehyde from acetylene, comprising pass ng an excess of acetylene gas in contact with an agitated mixture of metallic mercury and concentrated sulphuric acid and water, mamtaining the temperature of the mixture at between 70 and 80 C., and gradually adding ferric oxide to the mixture, so as to maintain the catalyzing action of the mercury indefinitely, at certain intervals and at the rate at which ferrous oxide is formed.

Witness ALPHONSE NICOLAS. 

